1. Field of the Invention
The present invention relates to the processing of semiconductor nanowires.
2. Background of the Invention
Nanowires are drawing tremendous interest due to their unique properties like high surface to volume ratio and dimensionality. Controlled nanowire growth methods can reliably synthesize nanowires of varying composition and size. Furthermore, advances in nanowire assembly techniques have enabled devices based on nanowires to be realized. Semiconductor nanowires may be active constituents for electronics, chemical sensors, and biological sensors.
The performance of semiconductor nanowires as active components for both nano-electronics devices and large area macroelectronics applications has been extensively investigated. Nanowires provide many advantages, such as scaling. Research has indicated that the performance of nanowire devices fabricated on flexible substrates is not significantly altered when repeatedly bent. Thus, silicon nanowires and thin film transistors (TFTs) based on nanowires can be used in flexible electronics instead of amorphous or polycrystalline silicon, or organic semiconductors. Such nanowire devices formed on lightweight and cheap flexible plastic substrates have many applications, such as displays, wearable electronics, mobile computing, information storage, and bio-detection. Other material systems based on nanowires, such as polymer-nanowire composites, have applications in a variety of fields.
Doping of silicon nanowires is required for the fabrication of electronic devices incorporating semiconducting nanowires. Doping of nanowires may be performed by introducing an appropriate dopant gas during metal-catalyzed growth of the nanowires. Even though modulation of doping profiles along the length of nanowires can be achieved, accurate alignment and positioning of the appropriately doped regions of the nanowires to build functional devices using currently known assembly techniques can be extremely cumbersome. Furthermore, different types of nanowire semiconducting materials can suffer from further problems. For example, the doping of germanium nanowires with boron in presence of B2H6 can result in cone-shaped nanostructures.
Ion-implantation is a reproducible and controllable method to introduce dopants into nanowires. Ion-implantation allows precise control of the amount of introduced dopants and the location of suitably doped portions of nanowires, which is essential to enable complex nanowire devices. However, damage to the crystalline lattice of nanowires occurs during ion implantation in the form of point and extended defects, and the dopant does not necessarily end up on lattice sites, which is required for it to be electrically active. As a result, a high temperature annealing step is required to activate implanted dopants and repair the implantation damage in nanowires. However, such high temperature processing can damage the substrates on which the nanowires are being processed, such as plastic substrates.
Thus, what are needed are systems and methods for enabling the processing of nanowires on temperature sensitive substrates, without the damage to the nanowires and substrates that can result using conventional processing techniques.